Filter cartridge

ABSTRACT

A filter cartridge for a household appliance, which is provided with a filter housing, the wall of which separates a housing internal side from a housing external side. A filter inlet opening which in the operation of the filter cartridge is open in relation to the external environment of the filter housing is provided, wherein a device for water conduction which comprises at least one filter chamber having at least one filter medium and terminates in a filter outlet opening for suctioning water from the filter cartridge is provided in the interior of the filter housing downstream of the filter inlet opening relative to the flow direction during operation, and wherein a filter connection element having an annular filter port which has an annular filter fixing face for the tight connection of the filter cartridge to a tank fixing face in the water tank is provided.

CROSS-REFERENCES TO RELATED APPLICATIONS

This Application is a Section 371 National Stage Application of International Application No. PCT/EP2021/074148, filed Sep. 1, 2021, and published as WO 2022/049133A1 on Mar. 10, 2022, and claims priority to German Application Nos. 10 2021 107 068.6, filed Mar. 22, 2021, 10 2020 123 004.4, filed Sep. 3, 2020, and 10 2020 123 005.2 filed Sep. 3, 2020, the contents of each are hereby incorporated by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective illustration of a tank bottom with an inserted filter cartridge according to the prior art.

FIG. 2 shows a perspective exploded illustration of a tank bottom with a centering element and a fastening ring, in one example.

FIG. 3 shows a perspective illustration of the tank bottom according to FIG. 2 with an installed centering element and an installed fastening ring.

FIG. 4 shows a top view of the tank bottom according to FIGS. 2 and 3 .

FIG. 5 shows a perspective illustration of the connection region of the filter cartridge viewed from the side, in one example.

FIG. 6 shows a perspective illustration of the connection region of the filter cartridge viewed obliquely from below, in one example.

FIG. 7 shows a perspective illustration of a filter cartridge cut open at the level of the filter port, inserted into a tank bottom, in one example.

FIG. 8 shows a perspective illustration of a filter cartridge cut open at the level of the guide grooves, inserted into a tank bottom, in one example.

FIG. 9 shows a perspective illustration of a filter cartridge inserted into a tank bottom, in one example.

FIG. 10 shows a perspective illustration of the centering element, in one example.

FIG. 11 shows a sectional illustration of a tank bottom without a filter cartridge, with the water tank valve open, in one example.

FIGS. 11 a and b show two enlarged fragments from FIG. 11 to visualize a closable bypass line in the tank seal, in one example.

FIG. 12 shows a sectional illustration of a tank bottom according to FIG. 11 with an inserted filter cartridge.

FIG. 12 a shows an enlarged detail from FIG. 12 to visualize the closed bypass line.

FIG. 13 shows a schematic end view of a filter port according to one example.

FIG. 13 a shows an enlargement of a fragment from FIG. 13 .

FIG. 14 shows a fragment of the filter cartridge showing the connection region to illustrate a guiding aid by bevels on the connector, in one example.

DETAILED DESCRIPTION

The present disclosure relates to a filter cartridge according to the preamble of claim 1.

Filter cartridges are typically used in water-carrying household appliances with a water tank, in particular in beverage machines such as coffee machines, tea machines, etc., in order to improve the water quality in accordance with the intended application. Filter media for water softening, such as ion exchange resin, or to improve the taste, such as activated carbon, are often used in such filter cartridges. The metered addition of additives, e.g. for health or taste improvement, such as the addition of minerals or vitamins, etc., is already provided for in combination with filter media.

Water tanks of machines of this type according to the prior art typically have tank connection elements on the tank bottom with an annular tank sealing face for the tight connection of a filter connection element of the filter cartridge provided for such a water tank, which enclose a tank passage opening in the tank bottom for the water to flow from the filter cartridge and the water tank to the household appliance.

Such water tanks and filter cartridges are described, for example, in publications DE 10 2004 050 877 A1, EP 1 867 626 A1 and DE 197 17 056 C2.

To prevent unsuitable filter cartridges from being used, the tank connection elements have already been provided with coding elements so that only filter cartridges that match these coding elements can be used.

Document EP 2 138 078 A1 discloses a connection device for permanently connecting to a tank bottom, which has pocket-shaped connection elements for connecting to the tank bottom. These are connected with tank-proximal fixing means in such a way that they can no longer be released in a non-destructive manner from the tank. A filter cartridge is then to be inserted into this connection device in a replaceable manner, wherein the connection device and the filter cartridge have hexagonal coding structures.

In certain embodiments, which are disclosed for example in publications WO 2008/017492A2, EP 2 433 906 B1, EP 2 065 972 B1, EP 2 050 220 B1, EP 2 050 221 B1 and EP 2 050 218 B1, a polygonal shape of the seals and tank sealing faces was also used for coding, so that apart from the sealing function an additional coding and fixing function is also performed by the seal itself.

These embodiments have the disadvantage that the angular contour restricts the fixing function to the corners and at the same time the sealing function is made more difficult in comparison to a round contour.

An object of the present disclosure is therefore to refine such a filter cartridge in such a manner that the disadvantages mentioned are avoided and the fixing of the filter cartridge is improved.

Proceeding from a filter cartridge according to the preamble of claim 1, this object is achieved by the characterizing features thereof.

In the following, elements to be assigned to the filter cartridge are generally provided with the assigning word beginning “filter” and elements to be assigned to the water tank are provided with the assigning word beginning “tank”. Features of advantageous embodiments and refinements of the present disclosure are described below in such a way that they are not mandatory, but may be present.

A filter cartridge according to one example is provided with a filter housing, the wall of which separates a housing internal side from a housing external side, wherein an open filter inlet opening is provided for water to enter from the water supply without any further connection elements, which, accordingly when used in a water tank, in the operating position of the filter cartridge is connected to the tank interior. Downstream of the filter inlet opening relative to the direction of flow during operation, a device for water conduction is provided in the interior of the filter housing, which comprises at least one filter chamber having at least one filter medium and terminates in a filter outlet opening for suctioning water from the filter cartridge. A filter connection element is provided with an annular filter port, which has an annular filter fixing face for fixing with respect to a tank-proximal tank fixing face.

As a result of this design embodiment, such a filter cartridge differs from filter cartridges of filter devices whose housings are connected tightly to water pipes of a water network with pressure-resistant connections and are thus integrated into the water network.

A filter cartridge according to one example is provided with a filter fixing face, the profile of which along the circumference of the annular filter port has a variable radius in relation to a central axis, so that the filter fixing face comprises radial convexities and/or radial concavities, wherein the convexities and/or concavities have a round profile, so that corners or edges are avoided.

As a result, the fixing function is improved and there are further possibilities for coding. This shape of the filter fixing face matches a corresponding shape of a tank fixing face, with the curvatures changing from the external side to the internal side and vice versa over the profile of the circumference making it more difficult or completely impossible to clamp a seal that is not adapted in shape onto a fixed tank-proximal contact surface.

The shape according to one example of the filter fixing face facilitates deformation of the filter port in the region of the filter fixing face because the radial convexities and/or concavities configure the shape of an annular spring, the circumference of the latter being able to be resiliently expanded or compressed. As a result of such a deformation facilitated by the variable radius, an improvement in terms of mechanical clamping and thus of fixing is possible, for example in comparison to a circular shape or a polygonal shape.

This filter fixing face is advantageously simultaneously provided as a filter sealing face. The spring effect of the annular spring here also improves the sealing action because the filter sealing face is pressed flat against the associated tank sealing face as a result of the spring pressure. Since corners or edges are also avoided by the described shape of the filter fixing face, this shape also improves the sealing function in addition to the resilient effect.

The resilient deformability of the filter fixing face can be improved in that the annular filter port of the filter connection element having the filter fixing face in the region of the filter fixing face has an annular wall having a wall internal side and a wall external side that run parallel or inclined to one another. Depending on whether the connector is pushed onto a tank fixing face or plugged into a tank fixing face, the wall external side and/or the wall internal side of the annular wall comprises or forms the filter fixing face.

Since in this embodiment the side of the wall opposite the filter fixing face has the same shape having a correspondingly larger or smaller circumference, this wall is configured overall as an annular spring. The annular wall then forms an annular spring with parallel or mutually inclined circumferential sides.

Furthermore, the annular filter port of the filter connection element can have an external and/or an internal wall which are/is beveled in relation to the vertical such that the external wall and the internal wall in terms of the operating position of the filter cartridge converge from the top toward the bottom. This results in a guiding aid which facilitates the introduction of the port into a gap between two tank-proximal faces of matching shapes, wherein the tank-proximal faces can at least partially form an inner and/or outer tank sealing face.

Accordingly, the beveled external wall can have an outer filter fixing face, and/or the beveled internal wall can have an inner filter fixing face so as to establish a fixing and optionally sealing form-fit with the corresponding tank sealing face.

In a refinement of the present disclosure the arrangement of the convexities and concavities of the filter fixing face is configured so as to be rotationally symmetrical over the circumference. This results in a restoring force of the annular spring that is evenly distributed over the circumference with more stable fixing and sealing of the filter cartridge in the installed position. A rotationally symmetrical configuration of the filter fixing face results when the convexities and/or concavities are configured to periodically oscillate around a circular line. This allows for different angular positions of the filter cartridge, making it easier to connect the latter. In addition, other technical functions can also be provided depending on the angle.

More stable fixing of the filter cartridge in the installation position is achieved in that the arrangement of the convexities and concavities of the filter fixing face is configured with the same angles over the circumference. The annular spring formed in this way can thus deform uniformly over the circumference both in the region of the convexities and in the region of the concavities.

The convexities and concavities of the filter fixing face can form a wave shape along a circular line, the wave shape consisting of an alternating sequence of convex circle segments forming the convexities and concave circle segments forming the concavities. A radially directed spring effect results from the profile following a circular line.

The spring action of the annular spring can be further improved if the concave and convex circle segments are connected tangentially at turning points at the transition between concave and convex curvatures.

In a specific embodiment of the present disclosure, the arc length of the convex circle segments is longer than the arc length of the concave circle segments. The swept angle of the convex circle segments is therefore greater than the swept angle of the concave circle segments. As a result, the tangential transition between the curves runs obliquely in relation to a central circle of the annular spring, so that no radially inward- or outward-directed force arises in the transitions during the deformation.

In a specific embodiment, the convex and the concave circle segments have the same segment radius. This results in a comparable force distribution within the segments during deformation.

The circle segments can be disposed in such a way that the convex and the concave circle segments lie within an outer envelope circle and outside an inner envelope circle, with the circle centers of the convex circle segments lying within the inner envelope circle and the circle centers of the concave circle centers lying outside the outer envelope circle. This shape results in a flat profile in relation to the envelope circles or circle segments running along a center line between the envelope circles, as a result of which the widening or shrinking of the annular spring is facilitated.

A good function has been shown when the radius of the inner envelope circle is between 5% and 15% of the radius of the outer envelope circle.

Furthermore, it has proven to be advantageous if the radius of the convex and/or concave circle segments is between 20% and 35% of the radius of the outer envelope circle.

The spring effect of such a spring ring is further counteracted when the wall thickness between the external side of the wall and the internal side of the wall running parallel or inclined thereto is between 7% and 10% of the radius of the outer envelope circle.

In addition, a profile has been shown to be advantageous when the turning points between the curvatures of the concave and convex circle segments are closer to the inner envelope circle than to the outer envelope circle.

The filter fixing face can form an external face of the annular filter port of the filter connection element that points away from a central axis of the filter outlet opening. Such a filter port, despite the changing circumferential curvatures, is able to exert a resilient contact pressure outwards essentially over the entire circumference when it is inserted into an opening on the water tank with a correspondingly radially inward-facing tank fixing face in order to achieve the desired fixing effect. Conversely, when plugged onto a tank connector on the water tank with a correspondingly radially outward-pointing tank fixing face, a resilient contact pressure can be exerted inwards essentially over the entire circumference by a radially inward-pointing filter fixing face, in order to achieve the desired fixing effect.

In a particular embodiment of the present disclosure, a filter fixing face is provided both on the internal side and on the external side of the filter port, one or both of which simultaneously form a filter sealing face. Such a filter port can be inserted into an annular slot on the tank, the side walls of which each form a tank fixing face and/or a tank sealing face.

With a view to using an elastomer seal, it is advantageous for the annular filter port of the filter connection element, which has the filter fixing face, at least in the region of at least one filter fixing face provided as a filter sealing face to be composed of a plastics material which is more dimensionally stable in comparison to an elastomer at operating temperature.

As a result of this strength, the filter port of the filter cartridge by way of the filter fixing face remains capable of exerting a resilient contact pressure on a tank-proximal tank fixing face, so as to establish a firmly tensioned fit of the filter cartridge, on the one hand. Such fixing can take place on the internal and/or the external side of the filter port, for example.

On the other hand, such a filter port can also readily deform a tank-proximal elastomer seal on the water tank side such that said elastomer seal has a snug tight fit on the filter fixing face forming the filter sealing face. This deformation could likewise take place on the internal and/or external side of the filter port.

Depending on the embodiment, an elastomer seal deformable in such a way either can be provided on the inside or the outside, or be designed such that said elastomer seal has an annular slot into which the filter port can be introduced.

By deforming an elastomer seal, one or more other functions can also be brought about in addition to the fixing function and the sealing function. This can, for example, also be a hydraulic function such as a valve function or the like.

The sealing effect of the filter sealing face in conjunction with the tank sealing face is improved as mentioned above if the convexities and/or concavities have a round profile such that corners or edges are avoided.

A constellation that works very well has been found, for example, when six convexities and six concavities are provided along a circular line that has a diameter of less than 3 cm.

The filter inlet opening of the filter cartridge can be configured as an annular screen opening on the outside of the filter port, as a result of which the filter cartridge in the water tank is open to the water contained therein.

The filter cartridge is improved if a guide structure for guiding and receiving a water tank-proximal centering element is provided within the filter port. The filter cartridge can thus be aligned in the axial direction when it is inserted into the associated water tank and fixed in this alignment in the operating position.

If the guide structure has at least one guide groove running in the axial direction, i.e. parallel to the central axis, for accommodating at least one guide rib of the centering element on the water tank, the filter cartridge when it is inserted into the water tank, by way of this guide structure and in interaction with the associated water tank-proximal centering element, can be guided into at least one angular position and additionally fixed there by the axial movement.

In order to provide guiding and fixing in a number of angular positions, the guide structure can have a number of guide grooves distributed around the circumference for this purpose.

Good guiding of the filter cartridge into the desired angular position is obtained when the wall of the guide grooves is radiused in such a manner that the width of the grooves tapers from bottom to top in relation to the operating position. The guiding of the filter cartridge can also be improved if the walls of the guide grooves are radiused in such a manner that the width of the grooves tapers radially from the internal side to the outside. The combination of the two tapering groove shapes results in a type of funnel effect for a rib of a water tank-proximal centering element that enters such a groove.

The groove shapes mentioned can be configured, for example, by means of internal curvatures in a wall of the guide structure connecting the guide grooves.

An embodiment of the present disclosure is shown in the drawing and is explained in more detail with reference to the following figures.

FIG. 1 visualizes the usual configuration of a water tank 1 of a beverage machine, such as a coffee machine, for example a fully automatic coffee machine according to the prior art. The water tank 1 comprises a tank bottom 2 and water tank side walls 3, partially shown with dashed lines. A filter cartridge 4 with a filter housing 5 is inserted into the water tank 1. The connection between the tank bottom 2 and the filter cartridge 4 is realized via tank connection elements 6 on the water tank and filter connection elements 7 on the filter.

The filter cartridge 4 is located in the interior 8 of the water tank 1, i.e. during operation, it stands entirely or partially in the water stored in the water tank 1. A filter port 9 of the water tank 1 for connecting the water tank 1 to the beverage machine (not shown) protrudes from the lower side of the water tank 1.

Illustrated in FIG. 2 is a round fragment of the tank bottom 2, wherein provided are a fastening ring 10 and a centering element 11 for insertion into a recess 12 in the tank bottom 2. A tank valve body 13 with a seal 14 configured as an O-ring, from which two pins 15 protrude upwards, can likewise be seen in FIG. 2 . The fastening ring 10 also carries an elastomer seal 16.

In FIGS. 3 and 4 , the fastening ring 10 and the centering element 11 are installed in the tank bottom 2. It can be seen here that the pins 15 can pass through the centering element and thus form coding elements for coding the water tank in relation to the associated machine connection, by which the tank valve body 13 must be actuated when the water tank is inserted. It is also clearly visible in FIG. 4 that the elastomer seal 16 forming the water tank seal 17 is an annular seal which has a variable radius R along its circumference in relation to a central axis A, so that the internal face of the water tank seal 17 that forms a tank sealing face 18 comprises radial concavities 19 and radial convexities 20. The first tank sealing face 18 simultaneously serves as the first tank fixing face.

In FIG. 5 the connection region 21 of a suitable filter cartridge 22 is shown. A filter port 23 forms an inner ring surrounded by an outer ring 24 with axially extending projections 25 and recesses 26. Between the inner ring 23 and the outer ring 24 is an annular inlet screen 27 through which water enters the filter cartridge. The external face 28 and the internal face 68 of the filter port 23 are also provided with convexities 29 and concavities 30 to match the tank sealing face 18. The external face 28 and/or the internal face 68 of the filter port 23 can simultaneously serve as a filter fixing face.

In the view of FIG. 6 , in addition to the parts of the connection region 21 of the filter cartridge 22 described above, the special configuration of a guide structure 31 of the filter cartridge 22 for receiving the centering element 11 is shown. The guide structure has guide grooves 32 which are aligned with the edges 33 of a polygonal ring 34, in the present example with six guide grooves which are aligned with six edges of a hexagonal ring. In the sectional illustration with a view from above according to FIG. 7 , the sectional plane goes through this polygonal ring 34.

Inner curvatures 35 which lie between the edges 33 and the guide grooves 32 adjoin upward into the interior of the filter cartridge. The inner curvatures 35 form the side walls 36 of the guide grooves 32. Due to this arched shape, the walls 36 of the guide grooves 32 taper both in the axial direction upward (relative to the operating position) and in the radial direction from the inside to the outside. In the intersection point, when viewed from above according to FIG. 8 , the section plane runs at a height at which the guide grooves 32 are clearly configured. A riser pipe 37 is connected centrally on the internal side, through which the water entering the filter cartridge 22 is directed upward to the filter section.

In FIG. 9 the entire filter cartridge 22 is shown. In a filter housing 37, which has an optional lateral metering opening 38 and the water connection on the bottom described. The optional metering opening 38 is only provided in the case of an embodiment of the filter cartridge that is configured for dispensing additives, e.g. minerals, vitamins or the like, from a metering chamber accommodated in the filter housing 37 into the water reservoir. Since such a metering chamber is closed within the filter housing 37 with respect to the filter section, it has no further significance with regard to the filtration. A filter cartridge according to one example can therefore also be readily constructed without this metering chamber and its metering opening 38. In particular, the operating position can be seen in FIG. 9 , to which the statements above and below in this description relate.

A perspective illustration of the centering element 11 can be seen in FIG. 10 . The centering element is provided with a bottom plate 39 which, in the installed state, lies in a receptacle of the elastomer seal and peripherally engages said receptacle from behind. A centering mandrel 40 protrudes upward from the bottom plate 39 and has an annular external face 41 which also forms a second tank fixing face. This external face 41 has a radius that varies along the circumference in relation to the central axis A, so that this external face 41 also comprises radial concavities 42 and convexities 43. The external face 41 is thus adapted to a corresponding shape of the filter port 9.

For further adaptation, the concavities 42 and convexities 43 of this external face 41 are also configured to periodically oscillate around a circular line, and have a round profile. In the illustrated embodiment, six concavities 42 and six convexities 43 are provided along a circular line with a diameter of less than 3 cm, corresponding to the design of the illustrated embodiment of the filter cartridge 22. With a different filter cartridge, the adaptation of the external face 41 or the second tank fixing face must be modified accordingly.

All adaptations to the external face 41 of the centering mandrel 11 result in only an annular slot between the external face 41 and the elastomer seal 16 for inserting the filter port 23 being open in the installed state. This results in a further coding against the use of an unsuitable filter cartridge. In addition, in this way it is possible to support the filter port 23 on its internal side on the external face 41 of the centering mandrel 11. In this way, the contact pressure of the filter port on the elastomer seal 16 can be increased uniformly over the variable shape along the entire peripheral shape.

At least one upwardly projecting tooth 44 is provided above the annular external face. The one tooth or the plurality of teeth 44 are mounted on a gradation 45 of the centering mandrel 40. Further, elevations 46 in relation the gradation 45, which follow the shape of the external face 41, are attached at a distance from the teeth 44, so that a gap 47 remains between the teeth and the elevations 46. The tooth or teeth 44 and/or elevations 46 may prevent the use of an axial seal to bypass the coding. Furthermore, a passage opening 48 is provided above the external face 41, which leads to a tank passage opening when the centering element 11 is in the installed state. The filtered water of a filter cartridge 22 can be discharged from the water tank through this passage opening 48.

One or more bottom vents 49 are provided in the bottom plate 39 below external face 41. Unfiltered water can be directed out of the water tank through these openings in the bottom. Below the elevations 46 and within the wall bearing the external face 41 there is a cavity 50 for receiving the tank valve body 13.

Provided above the annular external face 41 are guide ribs 51 which can be beveled on their upper side as in the exemplary embodiment shown. The guide bevels 52 formed in this way help when inserting the guide ribs 51 into the guide grooves 32 of a filter cartridge 22. In the sectional view according to FIG. 4 , the guide bevels 52 of the guide ribs 51 in the attached filter cartridge 22 can be clearly seen.

The assembled components of the water tank 1 for the connection of a filter cartridge with and without a filter cartridge 22 are shown in FIGS. 11, 11 a, 11 b, 12 and 12 a . The fastening ring 10 is provided with a latching projection 53 with which it can latch on the tank bottom 2 by engaging behind a bottom rib 54 of the water tank. The elastomer seal 16 has a bottom section 55 which engages under the fastening ring 10 and thus holds the elastomer seal 16 with the fastening ring 10 on the tank bottom 2.

For sealing in relation to the tank bottom 2, the elastomer seal 16 has a sealing face, which in the present case is realized by a sealing bead 56. For the tight closure of the elastomer seal 16 in relation to the fastening ring 10, a circumferential sealing face can be provided at various points. In the exemplary embodiment shown, an annular seal 57 is provided which is formed on top of the elastomer seal 16 and seals with the latter in a sealing groove 58 of the fastening ring.

The elastomer seal 16 includes an outer ring 59 and an inner ring 60 which are integrally molded and connected to each other. The outer ring 59 and the inner ring 60 in terms of the shape thereof both follow circumferentially the variable radius of fastening ring 10, of the filter port 23 and of the elastomer seal 16 and the concavities and convexities formed thereby. The outer ring 59 is stepped and carries the annular seal 57 and the sealing bead 56. The outer ring 59 is also provided with one or more bypass openings 61 through which unfiltered water can enter the annular gap 62 between the outer ring 59 and the inner ring 60 in the direction of flow P1. In the installed state, the bypass opening 61 of the elastomer seal 16 is located directly after a bypass opening 63 in the fastening ring 11, which can also be seen in FIGS. 1 and 3 , for example. Through the bypass opening 63, unfiltered water can flow out of the annular gap 62 from the water tank 1 in the direction P2 into the corresponding beverage machine.

The inner ring 60 has a sealing lip 64 on its lower side, which is opposite a sealing face 65 on the outer ring 59. In the relaxed state of the elastomer seal 16, the annular gap 62 between the outer ring 59 and the inner ring 60 is open at the bottom, as can be seen in FIG. 11 , so that the unfiltered water guided in the bypass can flow out of the annular gap 62 in flow direction P2. In this state, the internal side 66 of the inner ring 60, which forms the water tank seal 17, in the downward profile is beveled inward. The design embodiment of the bypass is highlighted in the enlargements according to FIGS. 11 a and b .

When a filter cartridge 22 with the filter port 23 is inserted, the elastomer seal 16 is deformed so that the internal side 66 is pressed outward and runs essentially perpendicularly along the filter port. The sealing lip 64 is pressed onto the opposite sealing face 65, and thus the annular gap 62 and thus also the bypass through the bypass openings 61, 63 are closed. The deformation generates a contact pressure that presses the tank sealing face 17 against the filter sealing face 28 and at the same time the sealing lip 64 against the sealing face 65. This state is shown in FIG. 12 and FIG. 12 a .

The tank valve body 13 in FIG. 11 and in FIG. 12 , by a detent (not shown in more detail) of the associated machine is raised counter to a restoring spring 67 into the cavity 50 and is thus in the open position which corresponds to the inserted water tank. If the water tank is removed from the machine, the tank valve body 13 closes under the pressure of the restoring spring 67.

The tank sealing face 18 is formed by the internal side 66 of the elastomer seal 16 and at the same time represents a first tank fixing face 18. As mentioned above, a first filter fixing face 28 formed by the filter sealing face 28 rests on this side when the filter cartridge 5, 22 is in the inserted state, under a contact pressure that deforms the elastomer seal 16 in such a way that a fixing and sealing form-fit is achieved.

A second filter fixing face 68 (see FIG. 5 ), which is formed by the internal face of the filter port 23, is in contact with the external face 41 forming the second tank fixing face. This form-fit is also formed under a contact pressure. Due to the shape of the filter port 23 according to one example, this forms an annular wall 69 which can be widened in a resilient manner if necessary. This results in the possibility of tolerance compensation with good fixing, which is caused by the corresponding bracing. Due to the mutually parallel or mutually inclined shaping of the first filter fixing face 28 and a second filter fixing face 68, the annular, corrugated wall 69 of the connector 23 lying between them forms a corrugated annular spring 70. The second filter fixing face 68 can also act as a second filter sealing face.

The filter port according to the end view in FIG. 13 and the enlarged detail according to FIG. 13 a shows the wave shape described with convexities 29 and concavities 30. The annular wall 69 of the filter port 23 with a wall thickness W has the first filter fixing face 28 on the wall external side 71 and the second filter fixing face 68 on the wall internal side 72. The wall external side 71 and the wall internal side 72 run parallel in the view shown, but are beveled toward one another in the axial direction, which will be explained further below. The wave shape is therefore further illustrated by means of a center line 73 shown in broken lines.

The center line 73 undulates between an outer envelope circle 74, whose radius has the largest value of the variable radius, and an inner envelope circle 75, whose radius has the smallest radius of the variable radius of the wave shape. The convexities 29 and concavities 30 of the center line 73 form wave crests in the form of convex circle segments 76 and wave troughs in the form of concave circle segments 77. In the illustrated embodiment, all circle segments 76, 77 have the same segment radius S. The centers 78, 79 of the circle segments 76, 77 lie within the inner envelope circle 75 for the convex circle segments 76 and outside of the outer envelope circle 74 for the concave circle segments 77. The convex circle segments 76 and the concave circle segments 77 merge tangentially and are evenly distributed over the circumference, resulting in a rotationally symmetrical shape. In the exemplary embodiment shown, in each case six convex circle segments 76 and six concave circle segments 77 are provided, which alternately lie at an angular distance of 30°, i.e. the convex circle segments 76 lie at an angle α of 60° apart from one another and the same applies to the concave circle segments 77.

Due to the selection of the segment radius and the associated position of the associated centers 78, 79, the center line runs in a comparatively flat, curved, wavy manner around the center circle line 80. The center line 73 intersects the center circle line 80 at an obtuse angle β. As a result, the arc length of the convexities 29 is significantly longer than the arc length of the concavities 30, as a result of which the angle γ swept by the segment arc of the convexities 29 is significantly larger than the angle δ swept by the concavities 30. This shape improves the spring effect of the filter port 23.

For comparison, the drawing also shows circle segments 81 whose segment centers 82 lie directly on the center line 73. This profile, which is not realized in this embodiment, has significantly smaller segment radii and a profile that is essentially perpendicular to the center line 73.

A good spring effect has been shown with radii and wall thicknesses in which the radius of the inner envelope circle 75 is between 5% and 15% of the radius of the outer envelope circle 74 and the radius of the convex and/or concave circle segments is between 20% and 35% of the radius of the outer envelope circle 74. The wall thickness W between the wall external side 71 and the wall internal side 72 running parallel or inclined thereto (relative to the operating position) is preferably between 5% and 15% of the radius of the outer envelope circle 74.

In the example shown, the outer envelope circle 74 has a radius of approximately 11 mm and the inner envelope circle 75 has a radius of approximately 9.75 mm. The segment radius of the convex and concave circle segments is approx. 3.08 mm and the wall thickness between the wall external side 71 and the wall internal side 72 running parallel or inclined thereto is approx. 0.9 mm.

In FIG. 14 it can be seen that the external 71 - and/or the internal wall 72 of the filter port 23, which depending on the embodiment also form one or two filter sealing faces 28, are beveled by the angle ω1 or ω2 in relation to the vertical, so that they based on the operating position of the filter cartridge 4, 22 converge from top to bottom. This bevel or bevels by the angle or angles ω1 and/or ω2 form an insertion aid when inserting the connector 23 into the annular gap between the elastomer seal 16 and the external face 41 of the water tank 1.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

List of reference signs: 1 Water tank 2 Tank bottom 3 Water tank side wall 4 Filter cartridge 5 Filter housing 6 Tank connection element 7 Filter connection 8 Interior 9 Filter port 10 Fastening ring 11 Centering element 12 Depression 13 Tank valve body 14 Seal 15 Pin 16 Elastomer seal 17 Water tank seal/annular seal 18 Tank sealing face 19 Concavity 20 Convexity 21 Connection region 22 Filter cartridge 23 Filter port/inner ring 24 Outer ring 25 Projection 26 Recess 27 Inlet screen 28 Filter sealing face/external face 29 Convexity 30 Concavity 31 Guide structure 32 Guide groove 33 Edge 34 Polygonal ring 35 Internal curvature 36 Wall 37 Filter housing 38 Metering opening 39 Bottom plate 40 Centering mandrel 41 External face 42 Concavity 43 Convexity 44 Tooth 45 Gradation 46 Elevation 47 Gap 48 Passage opening 49 Bottom vent 50 Cavity 51 Guide rib 52 Guide ramp 53 Latching projection 54 Bottom rib 55 Bottom portion 56 Sealing bead 57 Annular seal 58 Sealing groove 59 Inner ring 60 Outer ring 61 Bypass opening 62 Annular gap 63 Bypass opening 64 Sealing lip 65 Sealing face 66 Internal side 67 Restoring spring 68 Second filter fixing face/internal face 69 Wall 70 annular spring 71 Wall external side 72 Wall internal side 73 Center line 74 Outer envelope circle 75 Inner envelope circle 76 Convex circle segment 77 Concave circle segment 78 Center 79 Center 80 Center circle line 81 Circle segment 82 Segment center 83 Turning point 84 Tank passage opening A Axis W Wall thickness S Segment radius P1 Flow direction P2 Flow direction 

1. A filter cartridge for a household appliance, which is provided with a filter housing the wall of which separates a housing internal side from a housing external side, wherein a filter inlet opening which in the operation of the filter cartridge is open in relation to the external environment of the filter housing is provided, wherein a device for water conduction which comprises at least one filter chamber having at least one filter medium and terminates in a filter outlet opening for suctioning water from the filter cartridge is provided in the interior of the filter housing downstream of the filter inlet opening relative to the flow direction during operation, and wherein a filter connection element having an annular filter port which has an annular filter fixing face for the tight connection of the filter cartridge to a tank fixing face in the water tank is provided, characterized in that the profile of the first filter fixing face along the circumference of the annular filter port has a variable radius in relation to a central axis, so that the first filter fixing face comprises radial convexities and/or radial concavities wherein the convexities and/or concavities have a round profile and in that the convexities and concavities form a wave shape along a circular line, wherein the wave shape is composed of an alternating sequence of convex circle segments, forming the convexities, and concave circle segments, forming the concavities.
 2. The filter cartridge as claimed in claim 1, characterized in that the filter fixing face is simultaneously provided as a filter sealing face.
 3. The filter cartridge as claimed in claim 1, characterized in that the annular filter port of the filter connection element, which has the filter fixing face at least in the region of the filter fixing face has a wall having a wall external side that runs parallel to a wall internal side and comprises or forms the filter fixing face.
 4. The filter cartridge as claimed in claim 1, characterized in that the arrangement of the radial convexities and radial concavities of the filter fixing face is configured so as to be rotationally symmetrical over the circumference.
 5. The filter cartridge as claimed in claim 1, characterized in that the arrangement of the convexities and concavities of the filter fixing face is configured with the same angles over the circumference.
 6. The filter cartridge as claimed in claim 1, characterized in that the convexities and concavities of the filter sealing face form a wave shape along a circular line wherein the wave shape consists of an alternating sequence of convex circle segments forming the convexities and concave circle segments forming the concavities.
 7. The filter cartridge as claimed in claim 1, characterized in that the concave and convex circle segments are connected tangentially at turning points at the transition between concave and convex curvatures.
 8. The filter cartridge as claimed in claim 1, characterized in that the arc length of the convex circle segments is longer than the arc length of the concave circle segments.
 9. The filter cartridge as claimed in claim 1, characterized in that the convex and the concave circle segments have the same segment radius S.
 10. The filter cartridge as claimed in claim 1, characterized in that the convex and the concave circle segments lie within an outer envelope circle and outside an inner envelope circle wherein the circle centers of the convex circle segments lie within the inner envelope circle and the circle centers of the concave circle segments lie outside the outer envelope circle.
 11. The filter cartridge as claimed in claim 1, characterized in that the radius of the inner envelope circle is between 5% and 15% of the radius of the outer envelope circle.
 12. The filter cartridge as claimed in claim 1, characterized in that the radius of the convex and/or concave circle segments is between 20% and 35% of the radius of the outer envelope circle.
 13. The filter cartridge as claimed in claim 1, characterized in that the wall thickness (W) between the wall internal side running parallel to the wall external side is between 5% and 15% of the radius of the outer envelope circle.
 14. The filter cartridge as claimed in claim 1, characterized in that the turning points of the curvature of the circle segments are closer to the inner envelope circle than to the outer envelope circle.
 15. The filter cartridge as claimed in claim 1, characterized in that the annular filter port of the filter connection element, which has the filter fixing face at least in the region at least of the filter fixing face provided as the filter sealing face is composed of a plastics material which is more dimensionally stable in comparison to an elastomer at operating temperature.
 16. The filter cartridge as claimed in claim 1, characterized in that the annular filter port of the filter connection element has an external wall and/or an internal wall which, in relation to the operating position of the filter cartridge, is/are beveled at an angle ω1 and/or ω2 to the vertical so that the external wall and the internal wall of the filter cartridge converge from top to bottom in a manner inclined to one another.
 17. The filter cartridge as claimed in claim 1, characterized in that the beveled external wall has an outer and/or the beveled internal wall has an inner filter fixing face. 